ifndef SymbolAsString

sclass symbol_Tester { // compares by text (case-sensitive)

  Symbol symbol;

  *() {}

  *(Symbol *symbol) {}

  public int hashCode() { ret symbol.text.hashCode(); }

  public bool equals(O o) {

    if (!o instanceof symbol_Tester) false;

    ret eq(symbol.text, o/symbol_Tester.symbol.text);

  }

  toString { ret str(symbol); }

}

sclass symbol_MasterTester { // compares by text (case-insensitive)

  MasterSymbol symbol;

  *() {}

  *(MasterSymbol *symbol) {}

  public int hashCode() { ret symbol.lowerCase.hashCode(); }

  public bool equals(O o) {

    if (!o instanceof symbol_MasterTester) false;

    ret eq(symbol.lowerCase, o/symbol_MasterTester.symbol.lowerCase);

  }

}

static WeakHashMap<symbol_Tester, Bool> symbol_map = unsyncedWeakHashMap();

static WeakHashMap<symbol_MasterTester, Bool> masterSymbol_map = unsyncedWeakHashMap();

endifndef

static Symbol symbol(S s) {

  ifdef SymbolAsString

  ret s;

  endifdef

  ifndef SymbolAsString

  if (s == null) null;

  synchronized(symbol_map) {

    // This is a trick that works because of how WeakHashMap compares keys.

    symbol_MasterTester masterTester = symbol_MasterTester(new MasterSymbol(s, true));

    O e = call(masterSymbol_map, 'getEntry, masterTester);

    symbol_MasterTester existingMaster = e == null ? null : ((WeakReference<symbol_MasterTester>) e).get();

    if (existingMaster == null)

      masterSymbol_map.put(existingMaster = masterTester, true);

    ifdef symbol_debug

    if (eqic(s, "Java"))

      print("existing master for " + s + ": " + existingMaster);

    endifdef

    // second lookup after master found

    bool isEq = eq(s, existingMaster.symbol.text);

    Symbol symbol = isEq ? existingMaster.symbol : new Symbol(s, existingMaster.symbol);

    ifdef symbol_debug

    //print("existing master text: " + existingMaster.symbol.text + ", eq=" + isEq + " => " + symbol);

    endifdef

    symbol_Tester tester = symbol_Tester(symbol);

    e = call(symbol_map, 'getEntry, tester);

    symbol_Tester sym = e == null ? null : ((WeakReference<symbol_Tester>) e).get();

    if (sym == null)

      symbol_map.put(sym = tester, true);

    ifdef symbol_debug

    if (eqic(s, "Java"))

      print("Symbol for " + s + ": " + symbolToStringFull(sym.symbol);

    endifdef

    ret sym.symbol;

  }

  endifndef

}

static Symbol symbol(CharSequence s) {

  if (s == null) null;

  ifdef SymbolAsString

  ret str(s);

  endifdef

  ifndef SymbolAsString

  if (s instanceof Symbol) ret (Symbol) s;

  if (s instanceof S) ret symbol((S) s);

  ret symbol(str(s));

  endifndef

}

static Symbol symbol(O o) {

  ret symbol((CharSequence) o);

}